The present invention relates to a granule inspection apparatus adapted to use in visual inspection of granules such as medicine (fine grain, granulated powder, and powder), electronic materials (ceramic powder), food (cereals, flour product such as bread crumbs) and selection and removal of defective and foreign matter.
Visual inspection and selection of granules of this type has been conventionally performed in a manner in which granules are placed in sheet form on a belt conveyor, visually inspected while being transferred, and defective granules and foreign matter is removed as it is found.
However, there were sufficient possibilities that differences in individual quality of inspectors, fatigue and other factors could have resulted in inconsistencies in accuracy of inspection, overlooked defective granules and foreign matter, and the reliability of inspection by such method was low. On the other hand, in order to improve the inspection accuracy, it is necessary to slow down the conveying speed of granules and spread them into sheet form as thin as possible, but such practice, if adopted, involved a problem that processing efficiency is caused to be extremely low.
Furthermore, because of the presence of human beings, there were also other problems that inspections must be carried out in an open environment while difficulties are involved in preventing attachment of dust to granules being inspected.
With an objective to solve such problems as above, a granule inspection apparatus is proposed in which an image pickup element is used to automatically conduct visual inspection of granules, selection and removal of defective granules and foreign matter, etc. For example, in Japanese unexamined patent publication No. 58-159882, an inspection device is disclosed wherein by means of a well-known lighting means used for a microscope etc. granules such as cereals are caused to fall spontaneously, these granules are lighted from one side as well as from opposite side, the quantity of reflected light and that of transmitted light are equalized, the image of granules is photographed from one side and processed to detect presence of defective granules and foreign matter whose lightness is different from that of nondefectives and thereby to select and remove such defective granules and foreign matter by means of an air gun etc.
However, because the granule inspection apparatus as described above was constituted such that granules simply fall spontaneously, it was difficult to form the thin falling layer of granules into a regular thickness and the inspection accuracy used to be unstable. There was further a problem that when a certain length of granules in sheet form had fallen, granules spread spontaneously causing the granule passage to become unstable, and in the case of fine particles, powder that flies up makes it difficult to select and remove defective and foreign matter so that such inspection apparatus cannot be put to use.